Problem w/ Two-step Authentication

Hi there,

I’m running a blog hosted on WordPress and one of our members is being asked a “verification code generated by your Authenticator mobile application”, he has this kind of two-step authentication in order to access the dashboard but the thing is we haven’t installed any plugin enabling two-step authentication so we don’t understand where has this come from… He can’t access the Admin page because of that, and he can’t receive any verification code on his telephone as he hasn’t given his phone number anywhere apparently… Is there a way for him to get rid of this double authentication so he can simply access the Admin with his IDs? Thanks!